Automatic road wheel steering system

ABSTRACT

A system for automatically turning a road wheel. The system utilizes a strut-type suspension including a cylinder connected at one end to a steering knuckle and a piston/piston rod assembly slidable within the cylinder. An actuator is mounted to a vehicle body and operatively connected to the piston rod so as to rotate the same. The piston rod is also operatively connected through a suitable connection to the cylinder so that rotary motion of the piston rod is carried to the cylinder. This causes swing motion of the steering knuckle and thus the road wheel. The actuator is disposed in surrounding relation to the cylinder to bring the system into a compact arrangement.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to systems for automaticallyturning road wheels and more particularly to, an automatic road wheelsteering system utilizing a strut-type suspension.

2. Description of the Related Art

A strut-type suspension, better known as MacPherson-strut suspension islight in weight and simple in structure and has, thus, been used in manycompact cars. A typical strut-type suspension includes a strut with itsupper end fixed to a vehicle body. The strut has its lower end a balljoint through which a control arm is attached to a spindle. A shockabsorber is built into the upper section of the strut, and a coil springfits around the shock absorber. See "6th edition, Brakes, Suspension,and Steering" by William H. Crouse and Donald L. Anglin (McGraw-HillBook Company).

Japanese utility model publication No. 59-94976 discloses a strut-typesuspension having a shock strut with its upper end rotatably attached toa vehicle body through a suitable bearing assembly, and its lower endhaving an integral spindle on which a wheel is mounted. A system isprovided to automatically turn each steerable wheel. This systemgenerally includes an electric motor attached to the lower side of thevehicle body adjacent to the strut. The output shaft of the motor isconnected to the strut through a flexible long shaft by which torque istransmitted to assist turning of the steerable wheel. However, there area few disadvantages to this system. It is complicated, and is subject todamage because of its location.

SUMMARY OF THE INVENTION

It is, therefore, an object of the present invention to provide anautomatic road wheel steering system which is compact and is preventedfrom being damaged.

According to one aspect of the invention, there is provided a system forautomatically steering a road wheel, comprising a strut-type suspensionincluding a cylinder, a piston rod reciprocable within the cylinder, anda piston attached to one end of the piston rod, a wheel support memberfixed to the cylinder and rotatably supporting the road wheel thereon,first means for rotating the piston about its axis, said first meansmounted to a vehicle body and operatively connected to the other end ofthe piston rod, and second means for axially guiding the piston rodwithin the cylinder and operatively connecting the piston rod with thecylinder so that rotary motion of the piston rod may be transmitted tothe cylinder.

In a preferred embodiment of the invention, the first means is in theform of an actuator as including a cylindrical stator mounted to thevehicle body and having a plurality of permanent magnets, a rotor sleeverotatably supported on the stator in coaxial relation and having a coil.The rotor is connected through a speed reducer to a drive member whichis, in turn, fixed to the upper end of the piston rod so as to rotatethe same. The piston has a plurality of radial vanes, each vane havingopposite side wings which are fitted within guides formed on the innerperipheral surface of the cylinder. This arrangement allows the pistonrod to both slide axially and rotate about its axis within the cylinder.Rotary motion of the piston rod is transmitted through the connection tothe cylinder, causing turning of the road wheel.

The actuator is disposed in surrounding relation to the upper section ofthe cylinder, rather than being separately from the strut-typesuspension as in the conventional system, thus bringing the system intoa compact arrangement.

BRIEF DESCRIPTION OF THE DRAWINGS

A better understanding of of the invention may be had by reference tothe following detailed description when taken i conjunction with theaccompanying drawings, in which:

FIG. 1 is a perspective view of an automatic road wheel steering systemconstructed according to the teaching of the invention;

FIG. 2 is a sectional view of the system as shown in FIG. 1; and

FIG. 3 is an enlarged sectional view taken along the line III--III ofFIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to FIGS. 1 and 2, there is shown an automatic road wheelsteering system generally indicated at 1 and including a strut-typesuspension 2. The strut-type suspension 2 has a shock strut 3 in theform of a cylinder. A spring (not shown) is separately provided, insteadof being mounted directly on the strut 3. It may be disposed between alower control arm and a vehicle body. The illustrated suspension isdesigned for the left rear road wheel. It will be understood that theform and arrangement of the suspension for the right rear wheel isreversely similar. It will also be understood that the system may beused for each driven front wheel.

The shock strut 3 is fixedly attached at its lower end to the upper endof a steering knuckle 5 by a bolt/nut assembly 6. The lower end of thesteering knuckle 5 is connected through a ball joint (not shown) to theouter end of a lower control arm 7. The inner end of the lower controlarm 7 is, in turn, pivotably connected to a crossmember 9 through apivot connection 11. When the vehicle moves over the road, the steeringknuckle 5 pivots up and down slightly. This causes the control arm 7 toswing up and down. The steering knuckle 5 receives a spindle or axis 13through a bearing assembly 15. The spindle 13 is fixedly connected atits one end to a wheel 17 and is drivingly connected at its other end toa drive shaft 19 through a universal joint 21.

In the illustrated embodiment, a piston/piston rod assembly is slidablyand rotatably received within the cylinder 3. More specifically, apiston rod 25 has three radial vanes 27 on its outer peripheral surface.Each of the vanes 27 has opposite side wings 29 which are slidablyreceived within corresponding three axial guides 31 formed at the innerperipheral surface of the cylinder 3. The piston rod 25 is attached atits lower end to a piston 33 and at its upper end to an actuator 35.

As best seen in FIG. 2, the actuator 35 generally includes a cylindricalstator 37 mounted to a vehicle body 39 through a mount assembly 41.Specifically, the mount assembly 41 has a flanged inner plate 43 fixedto the stator 37, a flanged outer plate 45 bolted at 47 to the vehiclebody 39, and an isolator 49 sandwiched between the flanges of the innerand outer plates. The stator 37 has a plurality of permanent magnets 50on its inner peripheral surface. Rotatably supported by the stator 37through a bearing assembly 51 is a coaxial rotor sleeve 53 whichsurrounds the cylinder 3 and having a coil 55. This rotor sleeve 53 isconnected to a drive member 57 through a planetary-gear system or speedreducer 59 of a conventional construction. The drive member 57 has acylindrical upper section 57a rotatably supported on the innerperipheral surface of the stator 37 through a bearing assembly 61 andconnected to the upper end of the piton rod 25, and a cylindrical lowersection or internal gear 57b connected to the upper section 57a througha ledge 57c and having a diameter greater than that of the upper section57a. The speed reducer 59 generally includes a sun gear 63 fixedlymounted onto the upper end of the rotor sleeve 53, and a plurality ofplanet pinions 65 disposed in mesh with both the sun gear 63 and theinternal or ring gear 57b.

In operation, as the rotor sleeve 53 is rotated with respect to thestator 37, the rotary motion is first carried through the speed reducer59 to the drive member 57. This causes rotation of the piston rod 25. Asthe piston rod 25 is in engagement with the cylinder 3, the cylinder 3is rotated together with the piston rod 25. The rotary motion of thepiston rod 25 then causes the steering knuckle 5 to swing eitherforwards or backwards. The wheel 4 is finally turned in response to theswing motion of the steering knuckle 5.

It is to be understood that the forms of the invention herewith shownand described are to be taken as illustrative embodiments only of thesame, and that various changes in the shapes, sizes and arrangements ofparts may be resorted to without departing from the spirit of theinvention as defined in the following claims.

What is claimed is:
 1. A system for automatically steering a road wheel,comprising:a strut-type suspension including a cylinder, a piston rodhaving a longitudinal axis and reciprocable within the cylinder, and apiston attached to one end of the piston rod; a wheel support memberincluding a steering knuckle fixed to the cylinder and rotatablysupporting the road wheel thereon; first means for rotating said pistonrod about its longitudinal axis, said first means being mounted to avehicle body and operatively connected to the other end of said pistonrod; and second means for axially guiding said piston rod within saidcylinder and operatively connecting the piston rod with the cylinder, sothat rotary motion of the piston rod may be carried to the cylinder andthe steering knuckle fixed thereto, thereby effecting steering of theroad wheel.
 2. The system of claim 1, wherein said first means isdisposed in surrounding relation to the upper section of the cylinder.3. The system of claim 2, wherein said first means comprises acylindrical stator having a plurality of permanent magnets, a rotorsleeve rotatably supported on said stator in coaxial relation and havinga coil, and a drive member operatively connected to said rotor sleeveand fixed to the upper end of the piston rod.
 4. The system of claim 1,wherein said second means comprises a plurality of guides formed on theinner peripheral surface of the cylinder, and a plurality ofcorresponding inserts formed on the outer periphery of the piston rodand fitted within said guides.